Analysis of scratch characteristics of automotive clearcoats containing silane modified blocked isocyanates via carwash and nano-scratch tests

The aim of this study was to investigate the scratch characteristics of automotive clearcoats based on an acrylic polyol resin, with butylated melamine and silane modified blocked isocyanates, using car-wash and nano-scratch tests.To scrutinize the effect of silane modified blocked isocyanate on the chemical and mechanical properties of clearcoats, with respect to changes in the crosslinking networks inside the clearcoats due to the curing reaction, dynamic mechanical analysis (DMA) and FT-IR analysis were performed. The scratch behaviors were analyzed via Amtec–Kistler car-wash and nano-scratch tests, accompanied with scratch images simultaneously visualized using atomic force microscopy (AFM) and scanning electron microscopy (SEM). The basic properties of various automotive clearcoats such as impact resistance, pencil hardness, solvent resistance, and stone-chip resistance, were also compared. The results showed that a close correlation existed between the scratch resistance data obtained from the car-wash and nano-scratch tests for clearcoats made from acrylic polyol resin, with melamine and silane modified blocked isocyanates. Also, all the mechanical properties, including scratch resistance, noticeably improved due to the increased crosslinking networks via the formation of urethane bonds, when the portion of silane modified blocked isocyanates was increased. This was verified from the surface profiles and images of the scratched clearcoats captured using AFM and SEM.     

Dual-curing behavior and scratch characteristics of hydroxyl functionalized urethane methacrylate oligomer for automotive clearcoats

UV–thermal dual-curable, hydroxyl- and methacrylate-functionalized urethane oligomers with different contents of unsaturated double bonds and hydroxyl groups have been synthesized and incorporated into automotive clearcoats to investigate their curing and scratch behaviors. Dynamic mechanical analyses (DMA) and FT-IR analyses were performed to observe the variation of the crosslinking networks that resulted from the chemical reactions by UV and thermal dual-curing operations with varying curing conditions, such as UV dose, thermal curing time, thermal curing temperature, and curing sequence. The scratch behaviors of dual-cured automotive clearcoats were analyzed via nano-scratch tests, accompanied with scratch images simultaneously visualized using scanning electron microscopy (SEM). The mechanical and chemical properties, such as impact resistance, pencil hardness, acid-etch resistance, and stone-chip resistance, of dual-curable clearcoats were also compared with those of UV mono-cure and 1 K thermal-cure clearcoats. The results clearly showed that the dual-curing process induced a considerably higher degree of crosslinking for the cured clearcoats prepared from the dual-curable oligomers, melamine crosslinkers, and photoinitiators. Their mechanical properties including scratch resistance were also noticeably improved via the UV–thermal curing sequence, which led to an increased conversion rate of double bonds compared with clearcoats produced using the thermal–UV curing sequence. The best conditions for high crosslinking density as well as high hardness and modulus were 2400 mJ/cm² at 150 °C for 10 min in the UV–thermal curing process. This result was corroborated from the reaction kinetics and surface images of the scratched clearcoats captured by SEM.     

Evaluation of durability of nano-silica containing clear coats for automotive applications

In automotive application, multilayer coating systems are typically used to guarantee protection from corrosion phenomena and aesthetic properties. A coating system's appearance and its durability is becoming increasingly important for automotive original equipment manufacturers. Clear coats are required to maintain long term aesthetic appearance, color and gloss stability to weathering and mechanical damage. One key property is scratch and mar resistance. The use of nano-fillers is a promising strategy to increase the abrasion resistance without affecting the optical clarity of high gloss coatings.     

汽车零部件电沉积锌-锰合金镀层进展

根据国内外关于电沉积锌-锰合金镀层的研究情况,从锌-锰合金电镀溶液的体系,镀液对电流效率的影响,锰质量分数为15%~70%的锌-锰合金镀层的耐腐蚀性能等进行了分析讨论。发现在不同体系的镀液中,通过添加剂成分、锰离子浓度和电流密度等工艺参数的调控可在比较高的沉积效率条件下获得所需锰含量的锌-锰合金镀层。认为这种兼具优良耐腐蚀性能和力学性能的合金镀层对于汽车零部件来说具有明显优势。     

Automotive waterborne surfacer with improved stone-chip resistance

A new type of water dispersible hybrid polymer has been developed comprising a mercapto functionalized poly(epoxy ester) core, onto which the shell, an acrylic chain, has been grafted. Synthesis and characterization of such a hybrid polymer are given in full detail. When applied to automotive primer/surfacer formulations, they exhibit high solids contents, good filling power, and good stone-chip resistance, both in the VDA and SAE tests as well as with a controlled acceleration stone thrower (CAST).     

Mechanical properties of glass fabric/polyester composites: Effect of silicone coatings on the fabrics

An experimental investigation was carried out to study the effect of a silicone coating on the mechanical properties of polyester/woven glass fabric composites, fabricated by resin transfer molding. E‐glass woven fabrics were coated with a silicone elastomer by solution dip coating. The effect of variation of silicone amounts on the impact resistance, toughness, and mechanical properties of the composite was determined. Short beam shear tests were performed to assess the effect of coating on the adhesion of the fiber to the matrix. The coated specimens exhibited worse interlaminar shear strength over that of uncoated fabrics. Three‐point bending tests were also performed to investigate the effect of the coating on flexural properties. Whereas flexural strength and Young's modulus decreased with increasing amount of coating, the toughness, represented by the area under the stress–strain curve, presented a maximum. Finally, notched Izod impact tests were carried out and the curve for the energy absorbed during impact versus the amount of coating also appeared to have a maximum, indicating an interesting slot for optimum impact performance. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1300–1308, 2004     

Radiation curing technology: An attractive technology for metal coating

The introduction of new tailor-made (meth)acrylated oligomers has extended the potential use of the radiation curing technology to metal coating applications where adhesion, flexibility and corrosion resistance are of prime importance. In this paper, we discuss the properties of three fairly simple clearcoat systems spanning a range of glass transition temperatures between ≈10 and 70 °C. The systems were obtained by combination of two original urethane acrylate resins and two reactive diluents.Practical performance tests typically used to establish coating profiles in the metal industry (i.e., mechanical testing, adhesion, salt-spray test, etc.) were performed on ultraviolet (UV)-coated galvanised steel. In addition, the barrier properties of coated steel panels were systematically investigated at different coating thicknesses using electrochemical impedance spectroscopy. These results are analysed in terms of relevant physico-chemical characteristics such as conversion, volume contraction, swelling, viscoelastic and tensile behaviour determined on free-standing coating layers of the three formulations.     

聚苯胺颗粒对水性环氧树脂涂层防腐性能的影响

以盐酸为掺杂剂、过硫酸铵为氧化剂、咪唑类离子液体为稳定剂,采用化学氧化聚合法合成了导电聚苯胺(PANI)颗粒,将其分散到水性环氧树脂(ER)中制成聚苯胺水性环氧防腐涂层,研究了聚苯胺颗粒对涂层防腐性能和机械性能的影响。结果表明,添加聚苯胺显著提高了水性环氧涂层的阻隔性能,信号频率f=0.01 Hz时,PANI/ER涂层的阻抗(|Z|f=0.01Hz)均高于纯ER涂层。添加5.0wt% PANI时ER涂层阻隔性能最好,浸泡0~168 h时|Z|f=0.01Hz稳定在约8.0×108 Ω?cm2,浸泡168 h后|Z|f=0.01Hz=7.5×108 Ω?cm2,远高于ER和其它PANI/ER体系。中性盐雾实验结果表明,聚苯胺赋予了涂层钝化腐蚀的能力,显著提高了涂层的防腐性能,且其添加量越高,防腐性能越好。弯曲和冲击实验结果表明,涂层的机械性能随聚苯胺含量增加先上升后降低,当聚苯胺添加量不超过5.0wt%时,涂层的机械性能优异,附着力和韧性均较好;PANI添加量增至7.0wt%时,ER涂层的脆性明显变大,机械性能下降。聚苯胺在水性环氧体系中的最宜添加量为5.0wt%,此时涂层的机械性能良好,综合防腐性能最优。     

Novel organic–inorganic hybrid coatings prepared by the sol–gel process: corrosion and mechanical properties

(Hyperbranched polyurethane‐urea)/[(3‐aminopropyl)triethoxysilane]‐ZnO (HBPUU‐APTES‐ZnO) hybrid coatings were synthesized using an inexpensive mixing technique by varying the APTES‐modified ZnO concentration. The mechanical and surface properties of the hybrid coating films were studied and compared with unmodified and modified ZnO. The corrosion, solvent and abrasion resistance show significant enhancement in HBPUU‐APTES‐ZnO hybrids and their properties are increased with increasing APTES‐ZnO concentration. This hybrid coating has opened up an opportunity for automotive topcoat application. Copyright © 2012 Society of Chemical Industry     

On the electrochemical and structural behavior of biologically degraded automotive coatings; Part 1: Effect of natural and simulated bird droppings

Environmental factors can potentially deteriorate automotive coatings. These include UV radiation, humidity, hot–cold shocks as well as aggressive chemical compounds. In addition, natural occurring materials such as bird droppings and tree gums are also enable to affect the coatings. The present work aims to study the degradation of an automotive coating system exposed to natural and simulated bird droppings. To this end, structural analysis of samples was studied using FT-IR spectroscopy, optical and atomic force microscopes. Also, the mechanical and electrochemical behaviors of coatings were investigated by DMTA and electrochemical impedance spectroscopy (EIS). It was found that the biological materials significantly affect the mechanical and chemical properties of the coatings, resulting in a decrease in corrosion resistance. A two-time constant semicircle was observed for degraded coatings after a short time as a result of electrolyte diffusion into the coating/metal interface. The behavior of the coatings was then discussed based on the formation of surface defects.     

Characterization of interphase adhesion in multi-layer coating systems

Multi-layer coating systems are the state of the art for painting of metal and plastic surfaces e.g. in the automotive industry. Utilizing such systems consisting of several specialized coating materials, a high adhesion and a good corrosion protection can be reached, along with good barrier properties, chemical and scratch resistance as well as appealing surface appearance. The interphase regions between single layers of such systems represent areas of a potential weakness, where a delamination and a premature coating degradation can start. To test in a short time the protective properties of the coating, a special hydrothermal cyclic loading test procedure was developed, which causes accelerated build-up of internal stress within the coating system. Using an electrochemical impedance spectroscopy with various optimized electrode geometries, it was possible to detect the early stages of coating degradation and to compare different coating systems. Internal stress measurements contributed additionally to a better understanding of the coating degradation.     

辐照水性聚氨酯的复合改性研究与应用进展

综述了辐照水性聚氨酯(WPU)最常用的多元改性方法,重点介绍了γ射线(Co-60)辐照WPU和紫外光(UV)固化WPU的改性方法。改性后的辐照WPU的耐候性和机械性能要远优于WPU,辐照WPU经改性后可应用于印花粘合剂、地板涂料、木器漆涂料和汽车漆膜等领域。最后展望了辐照WPU的发展前景。     

An improved accelerated weathering protocol to anticipate Florida exposure behavior of coatings

A new accelerated weathering protocol has been developed which closely replicates the performance of automotive and aerospace coating systems exposed in South Florida. IR spectroscopy was used to verify that the chemical composition changes that occurred during accelerated weathering in devices with a glass filter that produced a high fidelity reproduction of sunlight’s UV spectrum matched those that occurred during natural weathering. Gravimetric water absorption measurements were used to tune the volume of water absorption during accelerated weathering to match that which occurred during natural weathering in South Florida. The frequency of water exposure was then scaled to the appropriate UV dose. A variety of coating systems were used to verify the correlation between the physical failures observed in the accelerated weathering protocol and natural weathering in South Florida. The new accelerated weathering protocol correctly reproduced gloss loss, delamination, cracking, blistering, and good performance in a variety of diverse coating systems. For automotive basecoat/clearcoat paint systems, the new weathering protocol shows significant acceleration over both Florida and previous accelerated weathering tests. For monocoat aerospace systems, the new weathering protocol showed less acceleration than for automotive coatings, but was still an improvement over previous accelerated tests and was faster than Florida exposure.     

Enhancing the mechanical properties of an epoxy coating with rice husk ash, a green product

In this research, rice husk ash (RHA) —a carbon neutral waste product that is an abundant source of silica—was chosen as an innovative filler for epoxy paint. The influence of the RHA on different mechanical properties of the cured coatings (wear, hardness, and elongation) was investigated. Wear tests in pin-on-disc mode were carried out and followed by scanning electron microscopic observations to determine the wear mechanism for specimens with different values of carbon and silica according to their different colors as fillers for epoxy paint. Pencil hardness tests and bending tests were performed according to ASTM D3363 and ASTM D522 standards, respectively. Adding RHA (heat treated at 700°C) at two levels—10 and 20% weight fraction—to the unfilled epoxy paint increased the wear resistance, scratch resistance, and elongation of the filled coating compared to the unfilled epoxy coating.     

Gradient MoSi2-borosilicate glass high emissivity coating with enhanced contact and impact damage resistance

High emissivity coatings on fibrous insulation tiles played an important role in thermal protection systems and thereby intrigued many researchers; however, there was little emphasis on the mechanical properties of the coatings. In this study, a gradient MoSi₂-borosilicate glass coating with a dense surface layer and a porous interlayer was designed for mullite fibrous ceramics. Mechanical properties and structure parameters of the coating layers and the substrate were studied. The gradient coating was compared with a monolayer dense coating of the same composition and same surface density in contact damage resistance, impact resistance and emissivity. Compared with monolayer dense coating coated substrates, the gradient coating coated ones exhibited two times higher load bearing capacity in Hertzian indentation test at the same displacement of 1?mm; they appeared to be stiffer and harder at constant load of 20?N, and showed better impact resistance at impact energy range of 0.25–0.75?J in the falling weight test; besides, fatal radial cracks were not observed in gradient coatings after the tests. In addition, the gradient coating had higher emissivity (0.838) than the monolayer dense coating (0.816) because of the significant absorptivity increase and reflectivity decrease by small gradual slopes in the rough surface.     

Swelling behavior of polymeric membranes to metalworking fluids

In some working places, such as metal manufacturing or automotive services, mechanical hazards commonly occur along with chemical hazards, particularly metalworking fluids (MWFs). The presence of these chemicals could modify the properties of gloves made from polymeric materials and thus reduce their protective properties against chemical contamination (solvent, MWFs) and mechanical risks (puncture and cutting). This work focused on determining the swelling characteristics and the resistance of six polymeric membranes which were exposed to seven industrial MWFs. We found that the swelling tests can be used to classify the potential of coating polymers in descending order of their resistance to MWFs: nitrile, polyurethane > poly(vinyl chloride), neoprene > butyl, latex. The analysis by multiple linear regression showed, for the first time, that the density or the viscosity‐gravity constant of the fluid and Hansen's solubility parameters of the polymers have a significant impact on the swelling of polymer. For the first time, two new multiple regression models have been proposed, to predict the swelling phenomena of polymers under various MWFs with an accuracy of ≈80%. The effect of temperature on mechanical properties and morphology of material was also examined. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 45717.     

Evaluation of pre-treatment processes for HRS (hot rolled steel) in powder coating

Hot rolled steel (HRS) is used extensively in the automotive, agricultural and appliance industries. The corrosive response of HRS was investigated after it had been exposed to various surface treatments, prior to powder coating. The behaviour of three conversion coatings: zinc phosphate (ZnP), iron phosphate (FeP) and zirconium (Zr)-based nano-scaled, on HRS was studied. HRS is naturally covered with iron oxide scale and this was removed from the surface by mechanical and chemical processes, prior to the application of surface treatment and organic coatings. The following tests on differently treated panels were conducted to evaluate corrosion performance: adhesion tests such as, crosshatch, pull-off, and conical bending, SEM, XPS, salt spray and electro-chemical impedance studies were also performed. Good correlations were recorded showing that zinc phosphate conversion coating gave the best performance, and zirconium-based nano-structured conversion coating, was superior to that of iron phosphate conversion coatings on HRS.     

Oligomers in the evolution of automotive clearcoats: mechanical performance testing as a function of exposure

Automotive coatings must provide excellent resistance to chemical and mechanical damage in order to maintain a vehicle's long-term appearance and the owner's long-term satisfaction. The Automotive Industry and coating suppliers are partners in design and delivery of future coatings capable of meeting customer demanded performance. As a result of this partnership, new coating materials are being explored based on oligomer chemistry that show promise in providing improvements in both physical and chemical properties/performance and the long-term maintenance of those properties. Oligomeric systems are also useful in design of low VOC coatings. These supersolids coatings will be capable of meeting current and future air quality standards. In this paper measurement techniques for monitoring chemical and mechanical property changes, including cure rate, crosslinking, tensile properties, rheology and scratch and mar performance, were explored. Laboratory mar tests, wet and dry rub tests, which have been validated by commercial experience, are currently used as the basis for comparison of a coating's mechanical performance. QUV accelerated weathering was combined with micro-scratch experiments, atomic force microscopy, optical microscopy, image analysis and IR surface characterization techniques to provide correlation's between chemical composition and mechanical performance, and an indication of service life.     

Sea Buckthorn Oil Tocopherol Extraction's By‐Product Utilization in Green Synthesis of Polyurethane Coating

The focus of the present study is to utilize a by‐product obtained during extraction of tocopherols, a valuable vitamin E compound, from sea buckthorn (SBT) oil and in doing so find a reliable alternative to petrochemical based polyols. Bio‐based polyurethane (PU) is prepared by using SBT oil based fatty acid methyl ester polyesteramide polyols (SBTPEP) with toluene diisocyanate (TDI). The fatty acid methyl ester is converted to the corresponding fatty amide by reaction with diethanolamine. The formed fatty amide is then esterified with phthalic anhydride to synthesize polyesteramide polyol. Characterization techniques used to evaluate polyesteramide polyol are Fourier‐transform infrared spectroscopy (FTIR) and NMR. The cured PU coating is also put through various mechanical tests to analyze the physical properties. The cured PU coating shows good surface and mechanical properties. It shows a gloss value of 87.4 and passes impact, adhesion, and chemical resistance tests. It is hydrophobic which is evident from its contact angle of 100.2°. It has good thermal stability which is evident by its glass transition temperature of 53.9 °C. Use of phthalic anhydride contributes to the bio‐based characteristics of synthesized PU. Practical Application: The present study presents a synthesis route which has minimal dependence on hazardous feedstock by utilization of green feedstock. The results obtained from physical and mechanical evaluations favor the use of this PU formulation in the coating sector. The adhesion and impact strength test results show potential application in the industrial sector coatings where the applied coat must be able to withstand high levels of physical stress and strain. The presence of aromatic rings and oil‐based moiety, that is the fatty acid hydrocarbon chain, contributes to the hydrophobic nature of the PU coating. Hydrophobic coatings have tremendous application in various fields such as marine coatings, automotive, electronics, and decorative coatings. These are potential fields of application for the synthesized green PU coating obtained from tocopherol extraction by‐products.     

The effect of Ti and Si on the mechanical and electrochemical behaviors of the AlCrN coating deposited by CAPVD on 304SS

This study aimed to investigate the effect of adding titanium (Ti) and silicon (Si) elements on the mechanical and electrochemical properties of the AlCrN-based coating. For this purpose, a cathodic arc physical vapor deposition machine was used. Scanning electron microscopy, X-ray diffraction, and nanoindentation tests were utilized for morphological, microstructural, and mechanical characterization of the coatings. The hardness value and plastic deformation index of CrAlN-based coating increase with the presence of Si element. The mechanical properties improvement is attributed to the reduction of crystallite size as well as to the tendency of the coating structure to become amorphous. The specimens were subjected to 3.5 wt% NaCl solution to electrochemical impedance corrosion and potentiodynamic polarization tests. The results showed that by increasing the coatings’ titanium content, the coatings’ corrosion resistance improved. Moreover, by adding 3% and 5% of Si elements to the coatings’ composition, the corrosion resistance of the AlCrTiSiN coatings was enhanced by 35% and 78%, respectively. Improving the corrosion resistance of the AlCrN-based coatings by adding the Si element is attributed to the change in the microstructure and reduction in the porosity of the coatings.